Manufacture of antihalation layers



Oct. 5, 1937. G. WILMA NIiNS ET AL 72,095,018:

MANUFACTURE OF ANTIHALATION LAYERS Filed Oct'. 1, 1934 Light sensitive emutaz'on ta er A support anti Jwdatton layeraf elatz'ne contazim'n cy p z rotuulte par-tablet of I to Jae in diameter Zi cyht aemz'ttve em utsz'on tag er antz-/zatatz'oh layer" of elatz'ne contaz'nz'n p Z/WOZMJL ZZ particles of to Jze m diameter,

Lm-mmxmmmtw .3? I

sup vart light sensitive emuln'on; layer support INYENTfiSL r WM M ATTORNEYS Patented a. 5,1937

UNITED STATES PATENT OFFICE.

MANUFACTURE OF ANTIHALATION LAYERS Application October 1, 1934, Serial No. 746,474 In Germany October 4, 1933 3 Claims.

' Our present invention relates to the manufacture of anti-halation layers and more particularly to the manufacture of anti-halation layers from pyrolusite.

5 One of its objects is a process for the manufacture of improved anti-halation layers from pyrolusite. Another object is the improved antihalation layers. Further objects will be seen from the detailed specification following hereafter.

It is known practice to use so-called pyrolusite layers, consisting;-,of higher hydrated oxides of manganese in gelatin, as anti-halation layers. This pyrolusite is produced in the gelatin in colloidal form by causing potassium permanganate solution to act on gelatin or by reducing potasslum permanganate by means of manganous salts in the presence of gelatin or other colloid to form manganese dioxide. In neither case,

however, is the pyrosulite present in the form of pure manganese dioxide, but in the form of a mixture of strongly reactive hydrates of varying composition. The anti-halation layers and filter layers containing such a reactive pyrolusite, af=

fect adversely the photographic emulsion when they come into contact therewith.

According to this invention a photographically satisfactory anti-halation layer and filter layer is obtained on the one hand by bringing the size of the particles of pyrolusite to about 0.1 to 5 and on the other hand by thermally treating, for example, by an intense drying at about 100 C. to

160 C. the pyrolusite, so that no higher hydrates are present. Thus, for example, a suitable pyrolusite can be produced by reduction of potassium permanganate (with alcohol, for example) in aqueous solution. After the pyrolusite formed has been separated it is dried at about 130 C. It

may then, if necessary, be ground in known manher; and when a suspension of it in a colloid swellable in water such as gelatin or casein is cast as an anti-halatlon layer, the layer exhibits none of the harmful-effects on the photographic emulsion which are caused by colloidal pyrolusite in the gelatin.

The pyrolusite of the anti-halation filter layers according to this invention is soluble in the fixing bath so that the layers are decolorized in this bath.

The following examples when taken with the accompanying self-explanatory drawing illustrate the invention: v

32 grams of pyrolusite which have been prepared as above described and dried at C. and have a grain size between 0.2 and 4p. are suspended in a solution of 70 grams of gelatin in 1000 cc. of Water. This solution is cast on the back of a photographic film as in Figure 1 or as an intermediate layer between the light sensitive emulsion layer and the support to form an anti-halation layer as in Figure 2, or on the emulsion layer to form a filter layer as in Figlusite in the solution of a colloid swellable in water, and casting said suspension to form an antihalation layer or filter layer. v

2. A process of manufacturing anti-halation layers or filter layers whichcomprises producing pyrolusite from potassium permanganate by reduction, drying said pyrolusite at a temperature of about 130 C., disintegrating the dried pyrolusite to particles of about 0.1 to 5; diameter, suspending said disintegrated pyrolusite in the solution of a colloid swellable in water, and casting said suspension to form an anti-halation layer or filter layer.

3. A process of manufacturing anti-halation layers or filter layers which comprises producing pyrolusite from potassium permanganate by reduction, drying said pyrolusite at a temperature of about 130 C., disintegrating the dried pyro lusite to particles of about 0.1 to fiadiameter, suspending said disintegrated pyrolusite in a. solution of gelatin, and castingsaid suspension to form an anti-halation layer or filter layer.

GUSTAV WILMANNS. WILHELM SCHNEIDER. 

